Mobile communication technologies are evolving to provide higher-rate, higher-quality data services than the conventional systems and solve implementational issues. The second-generation digital cellular mobile communication systems improved the voice quality and the channel capacity of the analog cellular mobile communication systems and provided voice and low-rate data services. The third-generation IMT-2000 has provided not only voice services but also multimedia services such as video services and high-rate data services including Internet services. European W-CDMA (or UMTS), North American CDMA 2000 1× and 1× EV-DO, and CDMA 2000 1× EV-DV have been researched and developed as the third-generation communication technologies. The fourth-generation mobile communication technologies, following the IMT-2000, are expected to provide more convenient, higher-quality services at lower costs than the conventional technologies.
The 3GPP, undertaking UMTS standardization, is being standardizing an LTE system as the next generation mobile communication system of the UMTS. Herein, the LTE system is an OFDM-based communication system.
In this manner, mobile communication systems are evolving from CDMA-based communication systems to OFDM-based communication systems. Thus, mobile communication service providers are completing to acquire a frequency band for initiation of an OFDM-based mobile communication service. When the mobile communication service providers use a frequency band to provide a communication service, they must pay the fee for the use of the frequency band.
Thus, the mobile communication service providers reduce the frequency use fee by reallocating frequencies or by returning/rearranging unused frequencies or frequencies that are expected to be used less frequently.
If a service band changes due to the frequency return/rearrangement/reallocation, the mobile communication service providers must make a determination reflecting the service maintenance of a conventional system terminal and the spectral efficiency according to the introduction of a new system.
FIGS. 1A and 1B illustrate an example of the frequency band operation of a service provider.
FIGS. 1A and 1B illustrate the frequency arrangement in the case of using only a conventional system (e.g., a CDMA-based system). FIG. 1A illustrates an 860 MHz˜870 MHz band allocated for downlink (or forward link) communication, and FIG. 1B illustrates a 915 MHz˜925 MHz band allocated for uplink (or reverse link) communication.
A mobile communication service provider may change the frequency band operation of FIGS. 1A and 1B in order to introduce a new system (e.g., an OFDM-based system). For example, the mobile communication service provider may maintain the currently-used downlink band and return (or reallocate) the previously-used uplink band. If a service band changes, the MSs served in a conventional band must be discarded (or corrected). That is, the MS and the BS of a conventional system must be corrected to receive a service in a changed band. If an uncorrected (or undiscarded) MS attempts an access after the frequency rearrangement, an uplink signal of the uncorrected (or undiscarded) MS may cause an interference in the returned band.
What is therefore required is a scheme for preventing a problem that may be caused by an MS that is not corrected (or discarded) in a frequency rearrangement process.